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Comment by a_c | Hacker News Reader

Glad to see zeromq being brought up. It is a fine piece of software with exceptional performance. The popularity has waned in recent year, particularly after the passing of Pieter, a main advocate of this technology.

I think people now use more battery including solution, probably a task queue, something SaaS'd even. I wonder how popular is zeromq nowadays? Does your company use it, for what?

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I always use ZeroMQ as a messaging layer among components. It's simple, reliable, supports multiple languages, provides very high performance. And straightens your mind, too: by providing a limited set of bullet-proof topologies, it really makes you think about your message flow, and when you make all lego-pieces fit, you get software that runs with _years_ of uptime.

Is there something like zeromq (or build on it) that has guaranteed delivery?

You just send the message again periodically forever until you receive an acknowledgement message. I don't think you need "something" for this, it's a five-liner.

Alternatively, depending on your use case, you mark messages with sequence numbers, and fill the gaps upon receiver's request.

At-most-once delivery is easy in anything. At-least-once is hard from scratch but there are good tools (TCP, HTTP/3) and patterns (retry, acknowledgement, logical monotonicity) and it’s generally not back-breaking.

Of course what everyone wants is exactly-once, which is profoundly difficult even when you know the exact cast of characters in terms of problem domain and compute fabric.

Idempotent updates with retry and ack is a very popular compromise that’s usually pretty feasible.

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